Electrostatic control with compensation for coupling effects

Abstract

An electrostatographic printing machine having an imaging member with a surface voltage potential and a control system including first and second reference values. A sensor measures first and second surface voltage potentials that are compared to the first and second reference values to provide first and second error signals to control first and second process stations in the printing machine. A first compensator responds to the first error signal to provide a first weighted adjustment to the first process station and a second weighted adjustment to the second process station. A second compensator responds to the second error signal to provide a first weighted adjustment to the second process station and a second weighted adjustment to the first process station in order to compensate for coupling effects between adjustments to either the first or second processing stations.

We claim: 
     
       1. In an electrostatographic printing machine having an imaging member with a surface including a control system: a sensor to measure first and second surface voltage potentials,   a first control loop responsive to the first surface voltage potential measured by the sensor to provide a first adjustment to the printing machine,   a second control loop responsive to the second surface voltage potential measured by the sensor to provide a second adjustment to the printing machine, wherein the improvement comprises first circuitry responsive to the first surface voltage potential to effect the second control loop and second circuitry responsive to the second surface voltage potential to effect the first control loop wherein the first circuitry and the second circuitry include look up tables.   
     
     
       2. The electrostatographic printing machine of claim 1 wherein the first circuitry and the second circuitry include summing nodes. 
     
     
       3. The electrostatographic printing machine of claim 1 wherein the first circuitry and the second circuitry include weighted compensators. 
     
     
       4. The electrostatographic printing machine of claim 2 including a Direct Loop Compensator interconnecting said first and second surface voltage potentials to the summing nodes. 
     
     
       5. A printing machine having an imaging member with a surface including a control system comprising: first and second reference values,   a sensor to measure first and second surface voltage potentials of the imaging member the first and second surface voltage potentials being compared to the first and second reference values to provide first and second error signals to control first and second process stations in the printing machine,   a first compensator responsive to the first error signal to provide a first weighted adjustment to the first process station and a second weighted adjustment to the second process station, and   a second compensator responsive to the second error signal to provide a first weighted adjustment to the second process station and a second weighted adjustment to the first process station in order to compensate for coupling effects between adjustments to either the first or second processing stations wherein the first and second surface voltage Potentials are unexposed and exposed voltages on the imaging member.   
     
     
       6. The printing machine of claim 5 wherein the first process station is a charging station and the second process station is an exposure station. 
     
     
       7. The printing machine of claim 5 including a first summing node connecting the compensators to the first process station and a second summing node connecting the compensators to the second process station. 
     
     
       8. The printing machine of claim 5 wherein the sensor is an electrostatic voltmeter. 
     
     
       9. A printing machine having an imaging member and a control system comprising: a first reference value,   a sensor to measure a first characteristic of the imaging member, the first characteristic being compared to the first reference value to provide a first error signal to control process stations in the printing machine, and   first circuitry responsive to the first error signal to provide a first weighted adjustment to a first process station and a second weighted adjustment to a second process station wherein the first circuitry includes a summing node.   
     
     
       10. The printing machine of claim 9 including a second reference value, the sensor measuring a second characteristic of the imaging member, the second characteristic being compared to the second reference value to provide a second error signal, and second circuitry responsive to the second error signal to provide a first weighted adjustment to the second process station and a second weighted adjustment to the first process station. 
     
     
       11. The printing machine of claim 10 wherein the first and second characteristics are voltage potentials. 
     
     
       12. The printing machine of claim 9 wherein the first circuitry includes a weighted compensator. 
     
     
       13. The printing machine of claim 9 wherein the first circuitry includes a look up table. 
     
     
       14. The printing machine of claim 9 including a Direct Loop Compensator interconnecting the second characteristic to the summing node. 
     
     
       15. In a printing machine having process stations: a sensor to measure machine characteristics,   control loops responsive to machine characteristics to provide adjustments to process stations, and   circuitry responsive to a control loop providing adjustments to a first process station effecting adjustments to a second process station in order to compensate for coupling effects wherein the circuitry includes a look up table.   
     
     
       16. The printing machine of claim 15 wherein the circuitry includes a summing node. 
     
     
       17. The printing machine of claim 15 wherein the circuitry includes a weighted compensator. 
     
     
       18. A printing machine having an imaging member and a control comprising: a sensor to measure first and second surface voltage potentials,   a first control loop responsive to the first surface voltage potential measured by the sensor to provide a first adjustment to the printing machine,   a second control loop responsive to the second surface voltage potential measured by the sensor to provide a second adjustment to the printing machine,   first circuitry including a summing node responsive to the first surface voltage potential to effect the second control loop, and   second circuitry including a summing node responsive to the second surface voltage potential to effect the first control loop.